Crystal Growth & Design最新文献

Assembling donor–acceptor (D–A) systems has become an emerging strategy to develop prominent heterogeneous photocatalysts in organic transformation. Herein, by linker modification, a UiO-67-type mixed-ligand metal–organic framework (termed UiO-67-PE/BT) was fabricated with pyrene as the electron donor and benzothiadiazole as the electron acceptor. Benefiting from the ultrastability of UiO-type materials and the outstanding photoactivity of the D–A system, UiO-67-PE/BT can efficiently photocatalyze the selective oxidation of organic sulfides into sulfoxides under visible-light irradiation. The enhanced photocatalytic performance of UiO-67-PE/BT was attributed to the D–A interaction in UiO-67-PE/BT that improves the synergetic effect of photoinduced electron transfer and energy transfer processes to generate abundant reactive oxygen species (superoxide radical and single oxygen). This work provided a feasible platform for the development of the D–A system to improve the transformation of solar energy into chemical energy.

The role of Ba²⁺ kink-site nucleation and step growth for the kinetics of anisotropic barite-(001) growth and Ra²⁺ kink-site nucleation for the activation energy of Ra uptake into the barite structure was investigated by using atomistic modeling approaches. The simulations show that Ba²⁺ kink-site nucleation at the barite-(001) water interface has higher activation energies at acute- and obtuse-low positions than at acute- and obtuse-high positions. The states at the low positions can be considered more relevant for barite crystal growth due to their higher stability. Kink-site nucleation at the obtuse step is preferred over that at the acute step due to the more open step geometry, which requires less dehydration. The simulations of the Ba²⁺─step growth processes indicate a slow and uniform growth of the acute step and a faster anisotropic growth of the obtuse step. Ra²⁺ kink-site nucleation at barite-(001) exhibits increased activation energies due to lattice distortion, which is partially compensated by the easier dehydration of Ra²⁺ compared to Ba²⁺. A small influence of Ra²⁺ on the kinetics of (Ba,Ra)SO₄ growth can be assumed because the rate-limiting kink-site nucleation process occurs preferentially through Ba²⁺ attachment compared to Ra²⁺ attachment. However, a preferential uptake of Ra²⁺ over Ba²⁺ during step growth, which requires a higher dehydration than kink-site nucleation, is therefore likely.

Ba²⁺ attachment and Ra²⁺ uptake during (Ba,Ra)SO₄ growth at the barite (001)─water interface by kink-site nucleation and step growth according to this study. The size of the arrows indicates the probability of the corresponding events.

Two mixed-ligand metal–organic frameworks (MOFs), [Co₃(ia)₃(bppdo)(MeOH)]_n·n(DMF) (1) and [Mn₃(ia)₃(bppdo)(MeOH)]_n·n(DMF) (2), have been synthesized, where ia = isophthalate, bppdo = 1,3-bis(4-pyridyl)propane-N,N′-dioxide, MeOH = methanol, and DMF = N,N′-dimethylformamide. Single-crystal X-ray diffraction studies reveal that 1 and 2, based on a linear Co₃ and Mn₃ cluster, respectively, are isoreticular and isostructural and possess two-periodic frameworks consisting of linear trinuclear metal clusters. Variable-temperature single-crystal X-ray diffraction studies confirm single-crystal-to-single-crystal transformations (rarely observed for MOFs based on a linear Co₃/Mn₃ cluster) upon desolvation and subsequent hydration, despite significant structural changes occurring. The desolvated structures (1′ and 2′) show a drastic reduction in their void spaces (3.7 and 5.7% for 1′ and 2′, respectively, at 298 K) as compared to their as-synthesized structures (potential void spaces of 21.6 and 22.3% for 1 and 2, respectively, at 298 K). Despite the similar void spaces at 195 K that are also seemingly inaccessible, significant CO₂ sorption occurs at this temperature for 1′ and 2′, indicating that structural changes had to occur in order to accommodate the adsorbed CO₂ molecules. Water vapor sorption at 298 K also induces structural changes in 1′ and 2′ as confirmed by single-crystal X-ray diffraction studies. The structural transformations that occur during desolvation and sorption processes emphasize the remarkable dynamic nature of these frameworks in responding to their environment.

Two mixed-ligand MOFs, [Co₃(ia)₃(bppdo)(MeOH)]_n·n(DMF) (1) and [Mn₃(ia)₃(bppdo)(MeOH)]_n·n(DMF) (2), have been synthesized, where ia = isophthalate, bppdo = 1,3-bis(4-pyridyl)propane-N,N′-dioxide, MeOH = methanol, and DMF = N,N′-dimethylformamide. Variable-temperature single-crystal X-ray diffraction studies show that both ligands of the isoreticular, isostructural, 2-periodic MOFs undergo significant conformational changes, depending on the external stimulus, indicative of the flexibility of the MOFs allowing significant carbon dioxide (195 K) and water vapor sorption (298 K).